When anode conductors of chip type electrolytic capacitors are manufactured, an aluminum plate is electrochemically etched, and an aluminum electrode plate comprising an etching layer having pits formed in a variety of configurations is obtained. A dielectric film is then provided to the resulting pit surface, and the pits are filled with a solid electrolyte. A cathode conductive layer is then further provided to the solid electrolyte layer. During use, a voltage is applied to an electrolytic capacitor that has been configured in this manner.
In case the electrolytic capacitor has a large electric resistance; i.e. equivalent series resistance (ESR), a large amount of heat is generated during use. Not only does electrical current tend to be lost, but the design must incorporate auxiliary equipment in order to cause the resulting heat to dissipate. Electrolytic capacitors having a low ESR have accordingly been in demand.
In patent document 1, a proposal is made for obtaining an aluminum electrode plate for an electrolytic capacitor having a 220-μm-thick etching layer on one side. An aluminum plate having a thickness of 450 μm is used as a starting material and is etched under the following conditions described in paragraph (0041): “ . . . a solution of 2% aluminum chloride and 8% hydrochloric acid is used as the etching solution, and a treatment is performed wherein electricity is provided at a solution temperature of 30° C., a frequency of 50 Hz, and a current of 0.15 A until an etching layer of the desired thickness is formed.” (refer to patent document 1).
[Patent Document 1] Japanese Laid-open Patent No. 2004-319795.